Paleodemographic simulations are rare in the Maya region, because generally the skeletal collections do not represent well the ancient living population, are poorly preserved, and lead to flawed age-at-death estimations. The skeletal collection of Xcambó, however, is suitable for paleodemographic analysis and is large enough to enable comparison of paleodemographic trends between the Early (AD 250–550) and Late Classic (AD 550–750) periods. Three demographic simulations were generated; two relied on growth rates calculated from the site's previous archaeodemographic data, and a third simulation was based on a stationary scenario by applying Weiss's (1973) and Séguy and Buchet's (2013) models. All simulations indicate that Xcambó’s Late Classic population was growing faster than its Early Classic peers, with higher rates of survivorship and more severe mortality rates. We argue that the differences are more likely due to shifts in lifestyle and wealth than to environmental changes, as is confirmed by other bioarchaeological and skeletal indicators.

Emerald ash borer (EAB), Agrilus planipennis, is a serious invasive forest pest in North America responsible for killing tens to hundreds of millions of ash trees since it was accidentally introduced in the 1990s. Although host-plant resistance and natural enemies are known to be important sources of mortality for EAB in Asia, less is known about the importance of different sources of mortality at recently colonized sites in the invaded range of EAB, and how these relate to host tree crown condition. To further our understanding of EAB population dynamics, we used a large-scale field experiment and life-table analyses to quantify the fates of EAB larvae and the relative importance of different biotic mortality factors at 12 recently colonized sites in Maryland. We found that the fates of larvae were highly dependent on EAB life stage and host tree crown condition. In relatively healthy trees (i.e., with a low EAB infestation) and for early instars, host tree resistance was the most important mortality factor. Conversely, in more unhealthy trees (i.e., with a moderate to high EAB infestation) and for later instars, parasitism and predation were the major sources of mortality. Life-table analyses also indicated how the lack of sufficient levels of host tree resistance and natural enemies contribute to rapid population growth of EAB at recently colonized sites. Our findings provide further evidence of the mechanisms by which EAB has been able to successfully establish and spread in North America.

Laboratory studies were conducted to assess the effect of temperature on the survival, development, longevity and fecundity of Helicoverpa armigera (Lepidoptera: Noctuidae) at eight different fluctuating temperatures with an amplitude ±9 °C under constant photoperiodic conditions of 16:8 h (L:D). H. armigera achieved complete development from egg to adult emergence between mean 17.5 and 32.5 °C. At mean 35 °C, all newly hatched larvae died and at mean 15 °C entered diapause at pupal stage. The lower developmental thresholds of the immature stages were estimated by a linear model and ranged from 4.63 °C (pupal stage) to 7.69 °C (egg stage). The developmental thresholds estimated by a nonlinear model were slightly higher than those estimated by the linear model. Adult longevity and fecundity were reduced at mean fluctuating temperatures 17.5 and 32.5 °C, but tended to be independent of the pattern of temperature change at moderate temperatures. The maximum reproductive performance, 1130 eggs per female, was observed at mean 25 °C. The intrinsic rates of increase were positive, meaning that H. armigera could be expected to persist or increase in number between mean 17.5 and 32.5 °C, with the maximum value at mean 27.5 °C. H. armigera survives, develops and reproduces within a wide range of fluctuating temperatures, while it completes the above functions with different levels of success at different mean temperatures of diurnal variation. Comparison of our results with similar data from the literature involving constant conditions is discussed. This information will provide a better understanding of H. armigera phenology and population dynamics under natural conditions and is essential to understanding the ecological and evolutionary consequences of climate change on this important species.

Our research deals with the way that calendar time affects mortality patterns in the Spanish population, and how this information can be used to elaborate predictions. A description of the observed mortality evolution has been worked out using data from 1975 to 1993. We have used Heligman-Pollard Law number two to model the evolution of Spanish mortality over the period and using univariate time series analysis, we have obtained a prognosis for years 1994 to 2010.

The Argentine stem weevil (Listronotus bonariensis) was an economically important pest in New Zealand pastures until the release of the parasitoid Microctonus hyperodae. This contribution uses historical data to investigate the regulation of the pest populations prior to, and somewhat during, the establishment of this parasitoid in dryland Canterbury, New Zealand. Thus, a significant goal of this study is to provide an L. bonariensis population dynamics baseline for any future work that aims to analyse the full effects of M. hyperodae on the weevil, now that equilibrium with the weevil host has been reached.

The population dynamics of L. bonariensis, based on a life-table approach, were investigated using data collected regularly for eight years from populations in Canterbury, New Zealand. The key factor affecting end-of-season L. bonariensis density was found to be variation in second generation fourth instar prepupal and pupal mortality. This may have been caused by arrested development and ongoing mortality resulting from the onset of cooler autumnal conditions.

A compensatory response was found in recruitment to the second summer weevil generation, whereby the realised fecundity of the emergent first summer generation of weevils was found to be negatively related to the density of adult weevils per ryegrass tiller. This is the first time that this has been found via long-term population analysis of L. bonariensis, although indications of this have been found elsewhere in caging, pot and small plot experiments.

In this study, the effect of the parasitoid biocontrol agent Microctonus hyperodae on L. bonariensis population dynamics was unclear, as the analysis covered a period when the parasitoid Microctonus hyperodae was introduced and still establishing. It does, however, raise important questions for future analysis in terms of the interaction between parasitism and unrealised fecundity.

The results in this contribution also highlighted regional differences. Overwintering mortality of adult weevils in Canterbury was constant between years, whilst earlier studies in the North Island Waikato region indicated this mortality was density dependent. In addition, the availability of tillers in endophyte-free ryegrass pastures in Canterbury had no influence on egg and early-instar larval survival, which contrasts with the finding from endophytic Waikato pastures.

The goal of this paper is to examine and demonstrate that survival analysis, which has been a de facto standard in biomedical research since the 1990s but has not been widely adopted in entomology yet, should possess similar potential in entomological research. The following three objectives are set to achieve this goal: (i) addressing a fundamental issue – censoring or incomplete observations; (ii) demonstrating the application of survival analysis to analyze insect life tables; and (iii) applying survival analysis for hypothesis testing. The data used to demonstrate the applications is from our laboratory experiments, which recorded the development, survival and reproduction of 1800 Russian wheat aphids (Diuraphis noxia (Mordvilko), RWA) under 25 treatments of temperature and plant-growth stage. With regard to the first two objectives, besides examining the near ubiquitous existence of censoring in insect population research, we constructed and analyzed life tables of 1800 RWA individuals with survival analysis. We further demonstrate that there could be very significant differences in life table parameters, such as median development times with and without considering censoring. To the best of our knowledge, this is the first recognition in entomology that censoring, which is hardly avoidable, can cause significant systematical bias (ranging between 4–25%; table 1) in insect development data analysis. As for the third objective, the study shows that four statistics from survival analysis can be applied to testing the effects of covariates, such as temperature and plant-growth stage, on development and survival of the Russian wheat aphid. The advantages of survival analysis include the handling of censored observations, survival probabilities in the form of rigorous survivor function vs. simple survival rates, dynamic modeling of covariates effects on development and survival with a unified model structure, etc. The methods demonstrated in this article should also be useful for entomological research beyond insect demography, such as bioassay, assessment of natural enemies, the studies of insect behaviors, etc.

The life table statistics of six native Kenyan species/strains of Trichogramma and Trichogrammatoidea were established using a factitious host Corcyra cephalonica, Stainton (Lepidoptera: Pyralidae), at eight different temperatures (10, 15, 20, 25, 28, 30, 32 and 35°C) and two humidity levels (40–50 and 70–80%). The objective was to select insects with superior attributes for augmentative release against lepidopteran pests in horticultural crops. Both temperature and humidity affected developmental time and life table parameters of the parasitoids but temperature played a more critical role. Developmental time was inversely related to temperature. The intrinsic and finite rates of increase increased with temperature up to 30°C. Both net reproduction rate and intrinsic rate of increase were higher at the lower humidity. Temperature inversely affected generation time of parasitoid strains regardless of the relative humidity. Two strains of Trichogramma sp. nr. mwanzai collected from both low and medium altitudes and Trichogrammatoidea sp. nr. lutea from the mid-altitudes, were better adapted to both low and high temperatures than the other strains, as indicated by the high intrinsic and net reproductive rates, at both humidity levels. These three strains appear to be promising candidates for augmentation biocontrol against the African bollworm Helicoverpa armigera in Kenya.

Life table studies of Earias vittella (Fabricius) on different hosts in the Insect Biotech Laboratory, Department of Entomology, Dr PDKV Akola, revealed that survival (lx) of immature stages of E. vittella on different hosts was 0.65 on okra, 0.56 on cotton, 0.54 on semi-synthetic diet and 0.51 on mesta. The net reproductive rate (Ro), at the end of each generation, of E. vittella was 81.91 on okra, 56.70 on cotton, 53.02 on semi-synthetic diet and 36.63 on mesta (Hibiscus cannabinus L.). The net reproductive rate (Ro) followed the same order as the survival rate (lx) on the different hosts. The innate capacity for increase in numbers (rm) ranged between 0.0888 and 0.1334 females/female/day. In descending order, the rm values on different hosts were okra (0.1334), cotton (0.1111), semi-synthetic diet (0.1029) and mesta (0.0888).

Studies were conducted at Mtwapa, in the coastal area of Kenya, during the long and short rains of 1999 and 2000 to evaluate interaction of mortality factors in lowering Chilo partellus (Swinhoe) populations in diverse agroecosystems. Treatments consisted of hedgerows of leucaena only, gliricidia only, alternating rows of leucaena and gliricidia, and three plots without trees. During the cropping seasons, maize was planted between the hedgerows while a row of cowpea was planted between the rows of maize. One of the plots without trees was planted to an intercrop of maize and cowpea. The remaining two plots without trees were planted to maize alone, one of which was mulched. The treatments were laid out in a randomized complete block design with four replications. There was no evidence of enhanced mortality in the more diverse systems indicating that the vegetation structure and cultural treatments studied did not enhance activity levels of C. partellus mortality factors. The highest mortality occurred in the early and medium larval stages in all treatments. This mortality was attributable to ‘disappearance’, which represented mortality from sources other than parasitism. The total real generation mortality showed that from the initial cohort of first and second instar larvae, less than 10% of C. partellus survived to adult stage under field conditions in all the treatments. Mortality by Cotesia sesamiae Cameron and Cotesia flavipes (Cameron) was very minimal, indicating the parasitoids were not important mortality factors of C. partellus under the cropping systems studied. Their effects were also not influenced by the cropping systems studied.

This paper presents basic demographic parameters of African elephants (Loxodonta africana) living in and around Amboseli National Park, Kenya. The study was conducted from 1972 to the present and results are based on the histories of 1778 individually known elephants. From 1972 to 1978, the Amboseli elephant population declined and then increased steadily from 1979 to the present. Births occurred throughout the year but over 80% occurred between November and May. Birth rate varied from year to year with a pattern of peaks and troughs at 4- to 5-year intervals. The birth sex ratio did not differ significantly from 1:1. Mean age at first birth was 14.1 years, determined from a sample of 546 known-age females. Mean birth interval (n = 732) was 4.5 years for 255 females. Fecundity and calf survival varied by age of the females. Mortality fluctuated from year to year. Sex-specific mortality rates were consistently higher for males than females at all ages.

We investigate the implications of a dual approach to the graduation of the force of mortality based on the modelling of the exposures as gamma random variables, as opposed to the modelling of the numbers of deaths as Poisson random variables.

The stage-specific and age-specific survivorship of the immature stages of Anopheles gambiae Giles s. l. were studied in Baringo District Kenya, using vertical life-table methods.

Survivorship from first instar to adult emergence was 0.085, giving a mortality of 91.5% during the rainy season. However, survivorship dropped to zero (100% mortality) in the dry season.

Mortality was most severe in the first and second instars in all cases. Mean life expectancy increased significantly for larvae that survived beyond the first 3 days of life. Suspected predators of mosquito pre-imagines in the breeding sites were collected and counted. From their large numbers and diversity it was inferred that predation was probablyan important mortality factor.

The aim of this paper is to extend the analyses of our earlier work (Haberman & Bloomfield, 1988)by incorporating mortality rates of male children categorised by age and social class. Data recently made available in an annex to the Decennial Occupational Mortality Investigation are utilised to produce graduated mortality rates specific for age and social class and to extend the social class specific life tables down to cover the full age range.

In this paper it is demonstrated how recently developed statistical techniques designed to facilitate the joint modelling of the mean and dispersion are well suited to model the presence of duplicate policies in graduation.

Data from regular field samples throughout the life cycle for five generations of the legume pod borer, Maruca testulalis on cowpea crops at one site, and three generations at another, were used to construct life tables and through key factor analysis to determine the key mortality factor. The total mortality from egg to adult was 98.4–98.6% at site 1 and 98.2–99.4% at site 2. At both sites the highest mortality occurred between the eggs and the third instar larvae, whilst the fourth instar larvae suffered the lowest mortality. The commonest cause of mortality was classified as disappearance, followed by disease. Parasitism contributed minimally to M. testulalis mortality. At site 1 disappearance at the egg stage was the key mortality factor and was significantly correlated with the total generation mortality. At site 2, disappearance operating at the larva 1 and 2 stage was tentatively identified as the key mortality factor. The data from site 1 showed no significant correlation between population density and mortality at the same stage. This study provides the first detailed analysis of M. testulalis populations and should contribute towards developing control strategies for this important pest of cowpea.

Studies at ICIPE's Mbita Point Field Station (site 1) and a farmer's field in Lambwe Valley (site 2) in Western Kenya, revealed the presence of at least seven parasitoids, two predators, one nematode and several microorganic pathogens attacking Maruca testulalis on cowpea crop. Some parasitoids and pathogens were also recovered from M. testulalis cadavers collected on wild host plants of the pest. A pupal endoparasitoid, Antrocephalus sp. was the most predominant, while the pathogens Nosema sp. and Bacillus sp. caused the highest natural mortality on M. testulalis in this region.

Parasitoids and pathogens contributed 40.65 and 35.6% to the total generation mortality (K) at sites 1 and 2 respectively. Observed parasitism only contributed 3.25% at site 1 and 3.8% at site 2 of the generation mortality. Mortality due to disappearance which included predation accounted for 59.35 and 64.8% of K at the respective sites. Life table data and survival curves for the pest revealed high generation mortality (ca. 98%), most of which occurred in the early life stages of the pest. The results suggest a high potential for utilizing biocontrol agents in IPM of the pest.

It is demonstrated how existing actuarial graduation practice, used in the construction of life tables, can be extended to considerable effect by formulating the techniques within the generalised linear and non-linear modelling framework.

This note considers the mortality table functions, and shows that the usual formulae hold under less restrictive assumptions than those usually made. The foundations of the theory of multiple-decrement tables are also considered, in the context of probability theory.